This invention relates to a magnetic recording medium, and more particularly, to an improvement in a protective film on a magnetic layer of a magnetic recording medium of the hard type such as magnetic disks and drums.
Magnetic recording media used in cooperation with magnetic disk apparatus are generally known as magnetic disks or disk media and have the basic structure comprising a doughnut shaped substrate having a magnetic layer usually on each of its surfaces.
The materials of which the substrates of such magnetic recording media are made include two types, hard materials such as aluminum alloy and plastic materials such as Mylar as also used in magnetic tape media. In general, the former is called a magnetic disk of the hard type and the latter a flexible disk.
The magnetic recording media for use with magnetic disk or drum apparatus, particularly hard type magnetic disks encounter some problems of durability and abrasion resistance against mechanical contact with a magnetic head. To this end, magnetic recording media are usually provided with a protective film. Known as the protective film of such media are protective films of inorganic material and lubricating films of solid lubricant.
The inorganic protective films used in the prior art are formed from, for example, Rh and Cr as disclosed in Japanese Patent Publication No. 52-18001, Ni-P as disclosed in Japanese Patent Publication No. 54-33726, Re, Os, Ru, Ag, Au, Cu, Pt and Pd as disclosed in Japanese Patent Publication No. 57-6177, and Ni-Cr as disclosed in Japanese Patent Publication No. 57-17292. The commonly used solid lubricants are inorganic and organic lubricants including silicon compounds such as SiO.sub.2, SiO, and Si.sub.3 N.sub.4 as disclosed in Japanese Patent Publication No. 54-33726, polysilicic acid and silane coupling agents such as tetrahydroxysilane and polyaminosilane as disclosed in Japanese Patent Publication No. 59-39809, and carbon.
The conventional protective films formed on the magnetic layer from these materials are somewhat unsuccessful in enhancing the durability, abrasion resistance, weatherability, and corrosion resistance of the associated media and suffer from the phenomenon called grip that the head adheres to the medium surface.
In our copending application Ser. No. 943,329 filed Dec. 19, 1986, we proposed a topcoat layer on a magnetic recording medium, comprising an organic fluorine compound of the same type as used in the present invention and characterized by improvements in durability, abrasion resistance, weatherability, corrosion resistance and grip resistance. The present invention represents an advance over this copending application in that a more thin and uniform topcoat can be realized.
Also, in our copending application Ser. No. 868,511 filed May 30, 1986, we proposed a topcoat layer for a magnetic tape having a metal magnetic thin film layer, the topcoat layer being formed from a fluorocarbon resin by sputtering or ion plating.